Cracking Clear

Some of you may remember issues I had in the past with clearcoat cracking sometime after it was dry.
Well it's happened again.
I had thought that it was down to using an enamel as a basecoat under automotive acrylic clear but this time I used automotive (Holts or Duplicolour) touch up paint as a base under Zero Paints candy over which I put the clear (candy allowed to gas out for at least 2 weeks indoors in the warm and clear thinned with same brand thinner).
Now, last time it happened it was enamel basecoat followed by candy followed by clear.
In both cases I polished with Kitten cutting compound followed by Meguiers Scratch X 2.0.
So, either the Zero Paints candy is reacting with the clear or it's solvents inthe polishes.
Don't know which but the cracking didn't appear until I had polished the body. Clear had been allowed to gas out for a week before polishing.
Any thoughts?

Is zero paint automotive? or hobby related? not familiar with them, but seems to be the common ingredient, i use holts/duplicolour undercoat, also some other branded automotive primer, and automotive clear with no problems, did have a problem with white undercoat once, threw it out and had no drama since. I also use automotive colours and the occasional nail polish with no problems. Good luck narrowing it down mate, can be frustrating.

Zero Paints are sold for car modelling through the hiroboy website. They describe them as "Acrylic Basecoats" and suggest use of their own 2 pack clear but i'm not willing to spray something that toxic with my set up (inadequate ventilation). They do also say you can use Tamiya TS13 & that "general automotive clear" shold be compatible.
The first 2 cases of cracking clear were when using it over enamel.
The 3rd one over candy over enamel and the 4th one over candy over automotive.
So really the only common thing between all 4 is the clear and the cutting compound/polish.
So far the latest cracking is confined to the roof & C pillers which are the parts that would flex most while polishing.
Maybe, when the warmth returns, i'll do some testing. Problem is that it takes time for the cracks to appear.
Until then i'll stick to other clears.

Good luck mate, it can be disheartening to have a paint job destroy its self, when you've done absolutely nothing wrong.

I'm scared to go out to the shed tonight incase it's got any worse...

Look, stuff happens and you learn. It's what life is all about. If everything was easy and perfect first time then what would be the point of doing it?

Fred, I'm by no mean's a paint expert & can only give you some advice based on my past/present experience, with what I use & how. I have, in my paint stash, most brands including Zero paints, Tamiya, Dupilcolour & HOK. Also in my polish stash I have Zero's 3 polishing compounds ( sold together ), Autoglym polish & nearly the full range of Meguiars polishes & their NXT 2.0 wax.

You've mentioned the types of colour & candy paint you've used ( acrylic/enamel & Laquer ) but you haven't mentioned what type of paint your clear gloss is?? From what I know Laquer based paints can be applied over any other, including acrylic / enamel but not the other way around... This will be the cause of your cracking.
On my current WIPS, the Camaro/Vette themed builds I've done/used the following paints/products...
On the Vette, Zero's white primer then base corvette yellow followed by their 2-pack gloss clear. I then wet-sanded with 6000grit polishing cloth. Followed it up by using Zero's coarse/medium/fine polishing compound & finally Auotglym's polish. The Camaro was slightly different because I had some body work to do including filling some areas with putty. After I did all the body work I primed with automotive ( in a can, avail @ supercheap auto ) plastic primer. After more sanding/priming & when the body was ready for colour I used Zero's Brilliant blue base coat. I applied the necessary decals, let sit & when ready I covered/sealed it all with Zero's 2-part matte clear. When dry I wet-sanded & gave it a light polish ( to get rid of all the little scratches made by the sanding cloth ) & then laid my stripes over the body, with Zero's yellow base coat. Once all that was dry I then cleared it with HOK's 2-part urethane clear. I've since wet-sanded it & so far have polished it with Zero's coarse/medium polish compound. I have some more to do as yet, with Meguiars No:2 fine cut, before I'll be happy, but so far there's no cracking. I'll post the results when I'm done.
As far as I know Duplicolour is a Laquer based auto paint ( not fully Laquer but mostly ) This may also be the problem considering you've used it as an undercoat to the Zero candy coats. I also have Zero's candy colours ( 3 all up ) as well as their undercoat silver. My advice to you is to strip it, if it's cracked again, & use wholly Zero based paints ( acrylic ) from primer to undercoat to candy & follow it all up with either 2-part urethane clear or Zero's 2-part clear. The problem is not the polish Guarenteed. It's definitely the different paints you've used in the wrong combination.
Cheers & good luck, Cliffo 👍👍

Duplicolour by Holts and PowerPlus by Holts are both Acrylic Lacquer. Water based paints are acrylic but not lacquer. You can put pretty much anything over acrylic lacquer including enamels but not the other way around. If you do and it works, good luck to you but I wouldn't do it.
Back to your problem Fred, I agree with Cliffo, not the polish, more likely the combo of paints.

The clear is Motospray Top Coat Clear Automotive Acrylic Lacquer Clearcoat and i'm thinning it with Motospray Aclac 20 Acrylic Thinner.
There has been no cracking when used over automotive touch up paint.
Everthing is primed and undercoated with White Knight primer & undercoat.
I've put some decals onto the latest cracked body (it's not that bad) and i'm going to put on some more clear over them so we'll see what happens to the cracks then.

I'm not using 2 pack as I don't want to spray anything that toxic.

I'm thinking the motospray is too hot for the whiteknight primer and that is what is cracking? Does it look like it's down at the primer level?

Fred, I wouldn't go down that route... Adding more clear. It won't fix the cracks, they'll re-appear. Try sanding it back first mate, level/even it all out if you can first then try re-clearing.
PS: Zero's 2-part gloss clear is no-where near as toxic as regular 2-part Urethane... Trust me. 😉 It's actually less fume-able than Tamiya Laquers.
Cheers Cliffo

That cheap crap White Knight primer enamel??? If so there's your problem, as Kirk said you cant paint acrylic over enamel.

Tubbo, Checko - you are both wrong.
White Knight is the best primer & undercoat i've found and i've been using them for years under EVERYTHING with no problems.
Plus the cracking is only in the clear and i've had no such problems with Tamiya clear which can react very badly with enamel.

Cliffo - i've decaled it now so sanding would be tricky...

However...

Despite what I've said about spraying toxic clear i've just bitten the bullet and have just ordered some Zero Paints 2 pack.
I'm just going to have to make sure I wear my gas mask (not something i'm that good at - a definate case of do what I say not what I do!).

No probs Fred, hope it all works out for ya mate & your build isn't buggered too much 👍 We all live & learn from mistakes, even though sometime's it ain't our fault 😉
Mate you'll be glad you're getting the Zero 2-part clear, it really IS less toxic than the HOK urethane stuff I've got. I ALWAY's wear a mask when painting, even though I have a great booth & great ventilation. It's never a good thing to get lead etc up into your nose & down into your lungs... 😉
Don't know what brush/size you use but a really good mate of mine suggested to me, to use 0.50mm nozzle with low pressure ( under 15psi ) when laying clear coats... I've got the Iwata HT Kustom Series brush & let me just say after taking his advice.... I had to do a lot LESS wet-sanding of the clear coats... Was very, very little, if at all, orange peel 👍👍
Cheers & good luck with it all mate, Cliffo

Thx mate.
I use 0.5 for pretty much everything but have been clearing on 30 psi.
Mine always looks great while it's wet but orange peels up as it dries.

It sounds to me like it could be differing curing rates between the basecoat and the clear. Possible reaction between slightly incompatible paints?
I know the Tamiya lacquers had a curing rate problem that didn't show up for months, then the paintwork would develop fine cracking all through it. I found out the best way to avoid the cracking was to either spray a clearcoat over the basecoat straight away (within seconds of the last basecoat) or to leave the basecoat to gas out for a few months before clearcoating.
These days I use Duplicolor almost exclusively (primer, basecoat, clearcoat) and I've never had a problem...

Chris.

No sweat Fred... Just try it under 15psi & see if that help's ? 😉